Tommo
11-27-2012, 02:08 AM
Many of the aquarium textbooks provide us with information on fish diseases, their identification and treatments. These textbooks also inform us of the dangers of treating aquarium water with more than one medication at a time and that water should be filtered through carbon, or water changed after treatments are completed or before we use other medicants etc.
However very few of the texts refer to fact that fish accumulate / or store medications in their body tissues and organs. That is; the texts fail to mention the possible adverse effects of this accumulation of medicants on the longer-term health of the fish. Similarly, many discussions on forums fail consider the bioconcentration, biomagnification or bioaccumulation of toxins / medications. So what do these terms mean and why are they important for an aquarist to understand the basic principals?
Basic definitions (relating to the medication of aquarium fish)
Bioconcentration is specific term which describes the uptake and accumulation of substances in tissues / organs from water (e.g. medicating water).
Biomagnification is an increase in concentration of a substance in tissues / organs from one link in a food chain to another (e.g. feeding medicated food).
Bioaccumulation however, refers to the build up of substances from all sources combined (e.g. medicating water and feeding medicated food etc.).
These terms refer to the build up over time of substances (e.g. medicants) in an organism’s tissues and organs faster than the rate that they can be excreted or metabolised. The problem we are faced with is that some of the chemicals that we use to medicate our fish, e.g. copper, malachite green etc, cannot be excreted or metabolised and therefore, accumulate in the tissues / organs of the fish. Even if we are using chemicals that are capable of being metabolised or excreted, we need to allow sufficient time for this to occur before considering additional treatments. Failure to do this may result overdosing or the accumulation of one medication with another in the tissues / organs of our fish. (There is a model for calculating this for those with a more scientific background than myself).
Implications
How many times have we misdiagnosed a disease and treated the symptoms with the wrong medicant? For example, many people start a treatment for gill flukes at the first sign of rapid breathing when in fact the problems may have been caused by poor water quality or protozoan infections etc. When we find out that the fluke medication isn’t working we may blame the product, filter the water through carbon, do a water change and try another product or, maybe decide that the problem has not been gill flukes after all and switch medication to treat another disease. The poor sick fish ends up with a cocktail of drugs accumulating in its tissues / organs!
Some diseases (e.g. Oödinium etc) are better treated to medications being added to the water and in such cases the calculation of dose rates is relatively simple. Also many of the branded products, sold for aquarium use, have a relatively wide safety margin built into them to reduce the possibility of overdosing. We clearly (I hope) need to be aware of the bioconcentration effects outlined above.
Other diseases (e.g. Capillaria etc) may be better treated by adding medication to the food. In this case however, the calculation of dosage rates is more problematic. Even if we can add the correct dosage to the food it is almost impossible control the amount of food a fish will eat etc. In this case we need to be aware of the effects of biomagnification . . .
How about the aquarist who uses the ‘belt and braces’ approach? Some people favour this overkill approach by medicating both water and food – a risky ‘double’ dose strategy unless we know exactly what we are doing. Therefore, the bioaccumulation effect needs to taken into consideration . . .
A final point to consider regarding the accumulation of medicants that cannot be metabolised: let’s say a fish that has been treated with toxic medicants in the past, it goes off its food and stops eating. The fish now gradually gets thinner and survives only by absorbing the ‘nutrients’ stored in its body tissues and therefore, starts to slowly poison itself with the accumulated toxins . . .
Hopefully, this missive gives members’ food for thought or should I say bioaccumulates in the brain? :D
However very few of the texts refer to fact that fish accumulate / or store medications in their body tissues and organs. That is; the texts fail to mention the possible adverse effects of this accumulation of medicants on the longer-term health of the fish. Similarly, many discussions on forums fail consider the bioconcentration, biomagnification or bioaccumulation of toxins / medications. So what do these terms mean and why are they important for an aquarist to understand the basic principals?
Basic definitions (relating to the medication of aquarium fish)
Bioconcentration is specific term which describes the uptake and accumulation of substances in tissues / organs from water (e.g. medicating water).
Biomagnification is an increase in concentration of a substance in tissues / organs from one link in a food chain to another (e.g. feeding medicated food).
Bioaccumulation however, refers to the build up of substances from all sources combined (e.g. medicating water and feeding medicated food etc.).
These terms refer to the build up over time of substances (e.g. medicants) in an organism’s tissues and organs faster than the rate that they can be excreted or metabolised. The problem we are faced with is that some of the chemicals that we use to medicate our fish, e.g. copper, malachite green etc, cannot be excreted or metabolised and therefore, accumulate in the tissues / organs of the fish. Even if we are using chemicals that are capable of being metabolised or excreted, we need to allow sufficient time for this to occur before considering additional treatments. Failure to do this may result overdosing or the accumulation of one medication with another in the tissues / organs of our fish. (There is a model for calculating this for those with a more scientific background than myself).
Implications
How many times have we misdiagnosed a disease and treated the symptoms with the wrong medicant? For example, many people start a treatment for gill flukes at the first sign of rapid breathing when in fact the problems may have been caused by poor water quality or protozoan infections etc. When we find out that the fluke medication isn’t working we may blame the product, filter the water through carbon, do a water change and try another product or, maybe decide that the problem has not been gill flukes after all and switch medication to treat another disease. The poor sick fish ends up with a cocktail of drugs accumulating in its tissues / organs!
Some diseases (e.g. Oödinium etc) are better treated to medications being added to the water and in such cases the calculation of dose rates is relatively simple. Also many of the branded products, sold for aquarium use, have a relatively wide safety margin built into them to reduce the possibility of overdosing. We clearly (I hope) need to be aware of the bioconcentration effects outlined above.
Other diseases (e.g. Capillaria etc) may be better treated by adding medication to the food. In this case however, the calculation of dosage rates is more problematic. Even if we can add the correct dosage to the food it is almost impossible control the amount of food a fish will eat etc. In this case we need to be aware of the effects of biomagnification . . .
How about the aquarist who uses the ‘belt and braces’ approach? Some people favour this overkill approach by medicating both water and food – a risky ‘double’ dose strategy unless we know exactly what we are doing. Therefore, the bioaccumulation effect needs to taken into consideration . . .
A final point to consider regarding the accumulation of medicants that cannot be metabolised: let’s say a fish that has been treated with toxic medicants in the past, it goes off its food and stops eating. The fish now gradually gets thinner and survives only by absorbing the ‘nutrients’ stored in its body tissues and therefore, starts to slowly poison itself with the accumulated toxins . . .
Hopefully, this missive gives members’ food for thought or should I say bioaccumulates in the brain? :D